Hydraulic tool

ABSTRACT

An hydraulic tool for mining and construction work designed to effect hydraulic reciprocating action of a piston to which a work implement is attached. The tool is illustrated as a rock drill. The tool avoids the usual impacting action and accompanying noise of a reciprocating piston hammer against a work implement. A motor operating independently of the reciprocating piston functions to rotate the piston and the work implement attached to the latter while the piston is reciprocating. A bulk oil accumulator forms part of the housing of the tool in which the piston reciprocates; and a power driven control valve determines the frequency of reciprocation and speed of the piston.

[ Nov. 11, 1975 1 HYDRAULIC TOOL [75] Inventor: Lester A. Amtsberg, Utica, NY.

[73] Assignee: Chicago Pneumatic Tool Company, New York, NY.

22 Filed: May 10, 1974 [211 Appl. No.: 468,899

Kollandsrud .1 173/105 Bailey 1. 173/105 Primary E.\'amilter.lames A. Leppink Attorney, Agent, or Firm-Stephen J. Rudy [5 7] ABSTRACT An hydraulic tool for mining and construction work designed to effect hydraulic reciprocating action of a piston to which a work implement is attached. The

52 US. Cl. l7 Int 2 tool is illustrated as a rock drill. The tool avolds the [58] Field of Search 173/105 134 usual impacting action and accompanying noise of a 8 reciprocating piston hammer against a work implement. A motor operating independently of the recip- [56] References Cited rocating piston functions to rotate the piston and the work implement attached to the latter while the piston UNITED STATES PATENTS is reciprocating. A bulk oil accumulator forms part of 3,132,707 5/1964 Alexander X the housing of the tool in the piston reciprofi -"g 133/105 cates; and a power driven control valve determines the 6 11/1971 g i g frequency of reciprocation and speed of the piston.

3,701,386 10/1972 Feucht 173/105 19 Claims, 5 Drawing Figures Q I 33\i 13 35 A \fi: l 32 H D J/ 2'7 3 -A l 38 I 2 6 1 j/ 39 TC) '13 ///l l l t m:' 9

U.S. Patent Nov.11, 1975 Sheetlof3 3,918,532

HYDRAULIC TOOL BACKGROUND OF THE INVENTION This invention is concerned with an improved hydraulically operable tool for mining and construction work, having a piston which is. reciprocable to forcefully impinge a work implement repeatedly against a work surface.

While the tool of the present invention is subject to wide application in mining and construction work in that it may utilize various work implements to meet the particular needs of the work involved, it is especially suited for use as a rock drill to which a string of drill rod is attached carrying a rock bit. Accordingly, the invention is illustrated herein as embodied in an hydraulically operable rock drill. As a rock drill, the took is especially suited for work in strata of medium hard rock at depths under 50 feet.

Mining and construction work tools, particularly rock drills, are known wherein a piston hammer is reciprocable by fluid power to repeatedly impact the work implement. In these known tools, the piston is a separate member which does not carry the work implement, but reciprocates as a hammer relative to it. The operation of these tools is accompanied by objectionable noise generated by the repeated pounding of the steel piston hammer against the steel work implement.

For the well bing of the workers involved, as well as the general community surrounding the area in which the work with such tools is being carried on, it is desirable that the objectionable noise attending their operation be reduced to an acceptable minimum.

Accordingly, it is a general object of this invention to provide an improved form of tool suitable for application in mining and construction work which is operable with an acceptable relatively reduced hearing level of accompanying noise as compared with the noise level attendant upon the operation of known tools.

It is another object of this invention to provide an hydraulically operable mining and construction work tool in which the conventionally employed action of pounding a piston hammer against a work implement has been eliminated.

It is a further object of this invention to provide, in particular, a rock drill tool having an overall improved structure as compared with known conventional rock drills.

In the present invention, these objectives are accomplished by the provision of a tool in which the work implement is reciprocated relative to the work by means of a piston instead of being pounded by the latter; by the provision of an efficient and practical arrangement for effecting hydraulic operation of the tool rather than pneumatic operation; and in other aspects as will later appear herein. The reciprocating piston with the work implement attached thereto, avoids the problem of noisy pounding of a piston hammer against a work implement. And hydraulic operation of the tool avoids the usual noise problems generated by the exhausting of spent air in conventional tools.

A feature of the tool of the present invention is an hydraulically floating and reciprocable piston having an extended piston rod to which the work implement is attached.

Another feature lies in the association with the piston of a power driven control valve which controls the application of hydraulic driving forces to the piston, as well as its operating frequency.

A further feature lies in the arrangement of a bulk oil accumulator in the housing of the tool, whereby operating oil feed channels required to effect reciprocation of the piston are in the nature of ports and short passages instead of hose lines, or lengthy passages. This close association of the source of operating fluid to the piston results in conserving the energy of the fluid, promoting efficiency in its operation, and in the minimizing of externally associated components of the tool.

Another feature lies in the aligned association of a rotation motor for effecting continuous rotation of the piston and the work implement carried by the piston whereby undesirable bulkiness of the tool is avoided, and a simplified drive train is provided between the motor and the piston which does not interfere with relative reciprocating action of the piston.

A still further feature lies in the provision of a decoupling unit in the drill string of the rock drill embodying the invention whereby, when excessive torque develops in the drill string because of a stuck condition of the rock bit, the drill string is enabled to rotate relative to the rock bit and thereby avoid excessive tightening of the drill string joints.

In accordance with the invention, there is provided an hydrualic reciprocating tool comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having a piston rod portion adapted to have a work implement attached thereto, a housing for the tool defining a bulk source of pressurized hydraulic fluid, the piston having a forward end surface area subject to application of pressure fluid from the source to move the piston in a return stroke direction and having an opposite relatively greater rear end surface area subject to application of pressure fluid from the source to move the piston in a work stroke direction, port means constantly exposing the forward end surface area of the piston to the pressure of fluid from the source, control valve means operable to intermittently expose the rear end surface area of the piston to the pressure of fluid from the source, and rotation motor means connected to impart rotation of the pistion.

The foregoing, as well as other objects, features, and advantages of this invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawing wherein an embodiment of the invention is illustrated, It is to be expressly understood, however, that the drawing is for purposes of illustration and description, and it is not to be construed as defining the limits of the invention.

BRIEF DESCRIPTION OF DRAWING In the accompanying drawing:

FIG. 1 is a view in longitudinal section of an hydraulic rock drill tool illustrating the invention;

FIG. 2 is a section taken on line 22 of FIG. 1;

FIG. 3 is a section taken on line 33 of FIG. 1 showing the control valve in its pressure position;

FIG. 4 is a section the same as that of FIG. 3, but showing the control valve shifted to its discharge position; and v FIG. 5 is a fragmentary detail section showing a tie coupler unit connecting the drill string with the rock bit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Reference is now direct to FIGS. 1-4 of the drawing wherein an embodiment of the invention is illustrated in an hydraulically operable rock drill tool. The tool has a general housing comprising a control valve block 11 fixed in suitable manner, as by bolting (not shown), to a rear wall 12 of a bulk oil reservoir block 13, the latter defining the forward portion of the housing.

Extending longitudinally through the lower half of the housing from its front to its rear end is a cylindrical bore 14 in which a piston cylinder 15 is fitted.

A piston 16 is hydraulically reciprocable in the cylinder by means of pressurized oil applied to it from a constantly pressurized bulk oil accumulator or reservoir 17 defined in the reservoir block section of the housing. The application of the driving forces of the pressurized oil is controlled by a control valve 18 that is reciprocable in the valve block section of the housing by suitable power means, shown here as a rotary motor 19 (FIGS. 1, 4). The reservior is of cylindrical form; it surrounds in eccentric relation a core portion 21 of the reservoir block section 13 of the housing, through which core the bore 14 containing the piston cylinder extends.

Providing the housing of the tool with an accumulator or reservoir containing a large quantity or bulk of pressurized oil is close proximity to the piston cylinder enables application of driving oil to the piston through passages and ports of a minimum length rather than through extended passages or hose lines as would otherwise be the case. In effect, the source of operating fluid for reciprocating the piston is located as close to the latter as possible. The advantageous resultant shortened flow lines enables swift application of operating fluid to the piston with a minimum loss of energy.

The reservoir is continuously maintained in a pressurized condition by means of a suitable conventional pump system 22 which functions during operation of the tool to pump oil from a sump tank 23 over a hose line 24 into an inlet 25 of the reservoir.

The piston 16 defines the head end of an extended piston rod 26 with which it is integral, the rod being of a smaller diameter than the piston. A forward rend of the rod projects externally beyond the front end of the housing; and it is adaptedas by means of a threaded section 27 -for connection with a work implement. Here, the work'implement is a rock bit 28 (as seen, for example, in FIG. 5) connected with the piston rod by means of a string of drill rod 29.

The tool is adapted along the underside of its housing by means of suitable brackets (not shown) to be supported for movement relative to the work along the usual carriage as provided in a conventional rock drill with feed means under the control of a diligent, skilled operator.

The material of the reservoir must be made of sufficient thickness to withstand high hydraulic pressure; however, the weight of the reservoir, plus the added weight of the hydraulic fluid contained in the reservoir, tends to stabilize the housing relative to the carriage by minimizing the effect of reaction forces and shock imparted to the tool during a drilling operation.

The piston rod is provided with a blow hole 31 which registers and communicates with the usual blow hole extending through the drill string and the rock bit for 4 conducting compressed air to the bottom of the hole being drilled.

The blow hole connects with radial ports 32 which are at all times in communication with a compressed air inlet 33. The latter is connected wth a supply of compressed air whereby during operation of the tool, air is fed to the blow hole (as needed) by means of conventional controls to clean the work hole of debris.

A fluid driven rotation motor 34 (here, hydraulically operable) is drivingly connected with the piston so as to transmit continuous rotation through the piston and the connecting drill string to the rock bit. The motor is operable indenpendently of the operation of the piston and is adapted to transmit its rotation to the piston without interfering with concurrent reciprocating action of the latter.

The motor is mounted by means of a supporting block 35 to the rear of the valve block section of the housing in axial alignment with the piston. This arrangement of the motor relative to the housing and piston enables a simplified driving connection of the motor with the piston. In this respect, a rotatable drive shaft extension or adapter 36 drivingly associates the motor with the piston and permits to the piston relative axial movement.

The piston is formed in its rear with an axial recess, the side wall of which provides a longitudinally extending slidable spline connection 37 with a forward end of the drive shaft adapter 36. The latter, in turn, has in its opposite end an internal splined driven connection 38 with the drive output shaft 39 of the motor.

The drive shaft adapter 36 is rotatable with the motor shaft 39 by means of the splined connection 38, but is restrained against relative axial movement by clamping means. The latter includes an annular flange 41 on the drive shaft adapter which has a rotative bearing relation between an annular shoulder of a cup bearing 42 and an opposed bearing face of a bushing 43. The bushing surrounds a rear extension of the drive shaft adapter and is seated in a recess of the motor mounting block 35. The latter (which is held fast, as by bolting) to the valve block, in turn holds the elements 42, 41, 43 in clamped relation to one another, allowing relative rotation of the drive shaft adapter 36 but restraining the latter against relative axial movement. In this arrangement, the piston is rotatable by the drive shaft adapted and is permitted axial sliding movement relative to the latter.

The piston is maintained during its operation by pressurized oil from the reservoir 17 in a floating condition clear of endwise contact with neighboring elements defined by a forwardly located annular internal shoulder 44 of the piston cylinder and further defined by a rearwardly located end 45 of the drive shaft adapter.

To the end of feeding pressurized oil to opposite ends of the piston to effect reciprocation of the latter, the reservoir communicates by a radial port 46 with the piston cylinder and communicates by means of a short passage, or port 47 (FIG. 2) with the control valve 18.

Port 46 communicates into the piston cylinder with an annulus area 48 surrounding the piston rod forwardly of an annular front end area 49 of the piston. Pressurized reservoir fluid continuously entering and filling the area 48 exerts a force upon the piston constantly urging the latter rearwardly in a return stroke direction. The control valve 18 'is reciprocable to alter nately cause the application and relief of pressurized reservoir fluid relative to an opposite and greater surface area of the piston as defined by the areas of the rear end wall 51 and recessed back wall 52 of the piston. By means of this arrangement, the rearwardly directed hydraulic force continuously acting upon the front end area of the piston is intermittently overcome by the hydraulic force alternately applied over the greater opposite rear areas of the piston, thus causing the piston to reciprocate.

The control valve is reciprocable in a bushing 53 (FIGS. 2-4) fitted centrally of a relatively longer bore 54 formed in the valve block. The bushing has inlet ports 55 which connect through an annulus 56 with the reservoir port 47; and has discharge ports 57 which connect through an annulus 58 with a discharge conduit 59 leading to sump 23.

The valve is of spool form having a groove 61 about its periphery. It functions as a three-way valve. In a first or pressure position of the valve (as in FIG. 3) the groove communicates the inlet ports 55 with a common annulus 62 opening into an area 63 of the cylinder at the rear of the piston. In this position of the valve, pressurized oil flows from the reservoir through the valve to the cylinder area 63 where it exerts a driving force against the end wall area 51 of the piston, and also passes through radial ports 64 and a recessed end of the adapter shaft toexert a further driving force against the back wall 52 of the piston, causing the piston to move forwardly on a work stroke.

In a reverse second or discharge position of the valve, as in FIG. 4, the groove 61 communicates the area 63 of the cylinder and the common annulus 62 with the discharge ports 57. In this position of the valve, the pressure of oil previously fed to the rear areas of the piston cylinder is relaxed through the discharge ports, and the oil in this area is forced to the sump as the piston is returned by the pressure of reservoir fluid in annulus 48 being exerted over its front end.

The control valve is reciprocable by suitable means, here illustrated by the rotary motor 19. The latter is driven by pressure of oil continuously being fed to it from the reservoir 17 through a suitable flow regulating valve 65 (FIG. 1) connected in a line 66 between an outlet 67 of the reservoir and an inlet of the valve motor 19. The motor is mounted to the valve block. Its output drive shaft 68 extends (as best seen in FIGS. 3 and 4) through the valve block into an area of the bore 54 adjacent one end of the valve bushing 53; and it connects by means of a scotch yoke or crank 69 with a necked end of the body of the control valve. Accordingly, the control valve is caused to be continuously reciprocated from one position to the other by the valve motor which is operating continuously during operation of the tool under the driving force of reservoir oil passing through the motor. Oil spent in driving the valve motor escapes from the motor over a line 71 to sump 23. A suitable manual control (not shown) is provided for opening or closing at the start, or close of operations respectively, the flow line 66 connecting the reservoir with the valve motor 19.

With each cycle of the valve motor, the control valve 18 is operable to cause the piston to travel through a work stroke and a return stroke. The position relationship of the inlet and discharge ports 55, 57 of the valve bushing 53 relative to the groove 61 in the valve is determined by a preadjustment of the axial position of the bushing 53 in the bore.54 relative to a position of the valve at a mid-point of its stroke. This is done so that the valve will be timely shifted from one position to the 6 other to allow for a predetermined percentage time of application of reservoir fluid force to the piston of a work stroke, and a predetermined percentage time for application of a reversal force of the reservoir fluid to the piston on return stroke.

The linear travel space in the cylinder 15 allowed to the piston 16 is defined between the internal shoulder 44 of the cylinder forwardly of the piston, and the end 45 of the adapter drive shaft rearwardly of the piston. This distance is, however, considerably greater than and more than ample for the normal amplitude of the piston so that deceleration of piston movement, occasioned by the shifting of hydraulic forces as consequence of the shifting cycle of the valve, will normally be sufficient to prevent the front end of the piston from abutting the cylinder shoulder 44 on a work stroke, and to prevent the recessed back 52 of the piston from bottoming against the end 45 of the adapter drive shaft. Further, normally before the reversal of hydraulic forces is effected to pressure the piston on a return stroke, the accelerating force of the piston will have been substantially dissipated upon its impingement with the work. On the return stroke of the piston, the acceleration of the latter and whatever is attached to it will prevail until the control valve shifts from its FIG. 4 discharge position back to its FIG. 3 pressure position. This will close the discharge ports 57 to the fluid being forced rearwardly by the returning piston and will open the inlet ports 55 for flow of reservoir fluid to the rear of the piston, the resultant reversal of forces will cause deceleration of the piston to zero followed by acceleration of the piston on a power stroke.

The frequency of piston reciprocation depends upon the regulated flow of reservoir fluid through the valve motor, and consequently upon the speed of the latter.

In FIG. 5, the drill rod or pipe string 29 is shown as including a decoupling unit 72 which provides a releasable rotary driving connection between the drill string and the rock bit.

Briefly, the decoupling unit includes an annular driving clutch member 73 carried by a coupling 74 threadedly attached to the drill string, and an opposed annular driven clutch member 75 carried by a rock bit rod 76 to which the rock bit 28 is attached. The rock bit rod has an axial sliding relation to the drill string and to the coupling, whereby the rock bit rod and drill string are constantly biased in opposite directions by the force of a clutch spring 77 so as to bring the clutch members axially into an engaged condition. This engaged condition is obtained when the drill string is drawn by the piston on a return stroke away from the work rock. In the engaged condition of the clutch members, the rotation being imparted to the drill string by the continuously operating rotating motor 34 is transmitted to the rock bit rod and rock bit, giving to the drill string and rock bit rotation in unison.

When the piston next moves forwardly on a work stroke, it moves the attached drill string downwardly to impinge the rock bit against the work rock. It also causes the drill string to simultaneously move downwardly relative to the rock bit rod against the resistance of the clutch spring sufficiently to carry the lower driving clutch member 73 axially, as in FIG. 5, out of engagement from the driven clutch member 75, and to abut a thrust transmitting end face 78 of the drill string against an opposed thrust receiving end face 79 of the rock bit rod, as in FIG. 5.

In this clutch disengaged or decoupled condition, the drill string is enabled to rotate relative to the rock bit rod and the rock bit, and the downward thrust of the drill string is caused to be transmitted through the abutting end faces 78, 79 through the rock bit rod to the rock bit.

By means of the decoupling unit the continuous rotation of the motor is transmitted only to the drill string when the rock bit is impinged against or embedded in the work rock; but his rotation is transmitted to both the drill string and rock bit in unison when the rock bit is freed from the work. In this matter, the excessive torque that would have otherwise developed in the drill string, and its undesirable tightening effect on the threaded drill rod joints in avoided. A more detailed description of the decoupling unit is set forth in my companion application Ser. No. 455,587, filed Mar. 22, 1974.

While the invention has been illustrated and described in detail herein, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design and arrangment of the parts thereof without departing from the spirit and scope of the invention. It is my intent of claim the invention, not only as shown and described herein, but also in all such forms and modifications as may be reasonably construed to fall within the spirit of the invention and the scope of the appended claims.

I claim:

1. An hydraulic rock drill comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having a piston rod portion, a rock bit, a drill string coupling the piston rod portion with the rock bit, a common source of pressurized hydraulic fluid, the piston having a forward end surface area subject to application of pressure fluid from the source to move the piston on a return stroke and having an opposite rear end relatively greater surface area subject to application of pressure fluid from the source to move the piston on a work stroke, port means constantly exposing the forward end surface area of the piston to the pressure of fluid from the source, power driven valve means for alternately exposing the relatively greater rear end surface area of the piston to the pressure of fluid from the source and to a pressure fluid discharge passage, the power driven valve means comprising a valve reciprocable between a position exposing the rear end surface area of the piston to the pressure of fluid from the source and a position exposing the said rear end surface area to the discharge passage, and a motor separate from the operable independently of the piston drivingly connected to reciprocate the valve from one position to the other.

2. An hydraulic rock drill as in claim 1, wherein the tool includes a housing defining a bulk reservoir for the source of pressurized fluid and having a bore in which the piston cylinder is located.

3. An hydraulic rock drill as in claim 2, wherein the reservoir has a port connecting with the cylinder forwardly of the forward end of the piston, and the reservoir has a second port connecting through the valve means with the cylinder rearwardly of the rear end of the piston.

4. An hydraulic rock drill as in claim 2, wherein the valve means includes inlet ports for communicating the rear end surface area of the piston with the source and discharge ports for communicating said area with a sump.

5. An hydraulic rock drill as in claim 4, wherein the valve means includes a reciprocable valve having a peripheral groove adapted on a forward stroke of the valve to communicate the inlet ports with the rear end surface area of the piston and adapted on a return stroke of the valve to communicate the discharge ports with said area.

6. An hydraulic rock drill comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having a piston rod portion, a rock bit, a drill string coupling the piston rod portion with the rock bit, a source of pressurized hydraulic fluid, the piston having a forward end surface area subject to application of pressure fluid from the source to move the piston on a return stroke and having an opposite rear end relatively greater surface area subject to application of pressure fluid from the source to move the piston on a work stroke, port means constantly exposing the forward end surface area of the piston to the pressure of fluid from the source, and power driven valve means for intermittently exposing the relatively greater rear end surface area of the piston to the pressure of fluid from the source; wherein the tool includes a housing defining a bulk reservoir for the source of pressurized fluid and having a bore in which the piston cylinder is located; wherein the valve means includes inlet ports for communicating the rear end surface area of the piston with the source and discharge ports for communicating said area with a sump; wherein the valve means includes a reciprocable valve having a peripheral groove adapted on a forward stroke of the valve to communicate the inlet ports with the rear end surface area of the piston and adapted on a return stroke of the valve to communicate the discharge ports with said area; and wherein a motor has a driving connection with the valve for reciprocating the latter from one position to the other.

7. An hydraulic rock drill as in claim 6, wherein the motor is hydraulically driven, and passage means is provided for causing flow of pressure fluid from the source to operate the motor.

8. An hydraulic rock drill as in claim 7, wherein flow regulating means is provided in the passage means between the source and the motor.

9. An hydraulic rock drill as in claim 1, including a rotation motor operable independently of the piston and having a rotary driving connection with the piston; wherein the first mentioned motor connected to reciprocate the valve is operable independently of any rotation that may be imparted to the piston by the rotation motor.

10. An hydraulic rock drill as in claim 9, wherein the rotation motor is mounted to the housing in axial alignment with the cylinder and piston.

11. An hydraulic rock drill comprising a housing, a piston cylinder in the housing, a piston hydraulically reciprocable in the cylinder having a piston rod portion adapted to have a drill string and rock bit attached thereto, a bulk oil accumulator chamber in the housing in surrounding relation to the cylinder providing a bulk source of constantly pressurized oil, the piston having a forward end surface of smaller area than its opposite rear end surface, a port communicating the accumulator chamber directly with the cylinder forwardly of the smaller area end of the piston and constantly exposing the latter end to the pressurized oil in the accumulator chamber; reciprocable valve means having a first port connection with the accumulator chamber, a second port connection with a discharge passage, and a com 9 mon port communicating with the rear end surface of the piston; and a motor connected to reciprocate the valve means for a first position communicating the first port with the common port to a second position communicating the common port with the second port.

12. An hydraulic rock drill as in claim 11, including a rotation motor having an output drive shaft means axially aligned with the piston, and the piston having an axially slidable driven spline connection with the drive shaft means, whereby the piston is enabled to have concurrently reciprocating axial movement relative to the drive shaft means and rotation with the drive shaft means.

13. An hydraulic tool comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having a piston rod portion adapted to have work implement attached thereto, a source of pressurized hydraulic fluid, the piston having a forward end surface area subject to application of pressure fluid from the source to move the piston on a return stroke and having an opposite rear end of relatively greater surface area subject to application of pressure fluid from the source to move the piston on a work stroke, port means constantly exposing the forward end surface area of the piston to the pressure of fluid from the source, and power driven valve means for intermittently exposing the rear end surface area of the piston to the pressure to fluid from the source; wherein the valve means includes inlet ports for communicating the rear end surface area of the piston with the source, and discharge ports for communicating said area with a sump; wherein the valve means includes a reciprocable valve having a peripheral groove adapted on a forward stroke of the valve to communicate the inlet ports with the rear end surface area of the piston and adapted on a return stroke of the valve to communicate the discharge ports with said rear-end surface area; and wherein a motor separate from and independent of the operation of the piston has a driving connection with the valve for reciprocating the latter from one position to the other.

14. An hydraulic tool as in claim 13, wherein the tool includes a housing defining a bulk oil reservoir for the source of pressurized fluid, and the housing provides a bore in which the piston cylinder is located.

15. An hydraulic tool as in claim 13, wherein the motor is hydraulically driven and passage means is provided for causing flow of pressure fluid from the source to operate the motor.

16. An hydraulic tool as in claim 13, including a rotation motor having a rotary driving connection with the piston.

17. An hydraulic tool comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having an externally extending piston rod adapted to have a work implement attached thereto, a housing providing a bulk reservoir of pressurized. hydraulic fluid for effecting reciprocation of the piston, the piston having a front end subject to application of pressure fluid from the reservoir to drive the piston on a return stroke and having an opposite rear end of a relatively greater area subject to application of pressure fluid from the reservoir to drive the piston on a work stroke, an outlet port connecting the reservoir with the cylinder constantly exposing the front end of the piston to the pressurized fluid of the reservoir, a second outlet port from the reservoir, a reciprocable control valve in the housing having a first position exposing the rear end area of the piston through the second outlet port to the pressure of fluid in the reservoir and having a reverse position exposing the rear end of the piston to a discharge port, and a motor separate from an operable independently of the piston to reciprocate the control valve from one position to the other.

18. An hydraulic tool as in claim 17, wherein the power means is an hydraulically operable rotary motor drivingly connected with the control valve and having a conduit connection with the reservoir for allowing flow of pressurized fluid from the reservoir to operate the motor.

19. An hydraulic tool as in claim 18, wherein a flow control regulator is provided in the conduit for regulating the operating speed of the motor and as a consequence the reciprocating frequency of the control valve. 

1. An hydraulic rock drill comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having a piston rod portion, a rock bit, a drill string coupling the piston rod portion with the rock bit, a common source of pressurized hydraulic fluid, the piston having a forward end surface area subject to application of pressure fluid from the source to move the piston on a return stroke and having an opposite rear end relatively greater surface area subject to application of pressure fluid from the source to move the piston oN a work stroke, port means constantly exposing the forward end surface area of the piston to the pressure of fluid from the source, power driven valve means for alternately exposing the relatively greater rear end surface area of the piston to the pressure of fluid from the source and to a pressure fluid discharge passage, the power driven valve means comprising a valve reciprocable between a position exposing the rear end surface area of the piston to the pressure of fluid from the source and a position exposing the said rear end surface area to the discharge passage, and a motor separate from the operable independently of the piston drivingly connected to reciprocate the valve from one position to the other.
 2. An hydraulic rock drill as in claim 1, wherein the tool includes a housing defining a bulk reservoir for the source of pressurized fluid and having a bore in which the piston cylinder is located.
 3. An hydraulic rock drill as in claim 2, wherein the reservoir has a port connecting with the cylinder forwardly of the forward end of the piston, and the reservoir has a second port connecting through the valve means with the cylinder rearwardly of the rear end of the piston.
 4. An hydraulic rock drill as in claim 2, wherein the valve means includes inlet ports for communicating the rear end surface area of the piston with the source and discharge ports for communicating said area with a sump.
 5. An hydraulic rock drill as in claim 4, wherein the valve means includes a reciprocable valve having a peripheral groove adapted on a forward stroke of the valve to communicate the inlet ports with the rear end surface area of the piston and adapted on a return stroke of the valve to communicate the discharge ports with said area.
 6. An hydraulic rock drill comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having a piston rod portion, a rock bit, a drill string coupling the piston rod portion with the rock bit, a source of pressurized hydraulic fluid, the piston having a forward end surface area subject to application of pressure fluid from the source to move the piston on a return stroke and having an opposite rear end relatively greater surface area subject to application of pressure fluid from the source to move the piston on a work stroke, port means constantly exposing the forward end surface area of the piston to the pressure of fluid from the source, and power driven valve means for intermittently exposing the relatively greater rear end surface area of the piston to the pressure of fluid from the source; wherein the tool includes a housing defining a bulk reservoir for the source of pressurized fluid and having a bore in which the piston cylinder is located; wherein the valve means includes inlet ports for communicating the rear end surface area of the piston with the source and discharge ports for communicating said area with a sump; wherein the valve means includes a reciprocable valve having a peripheral groove adapted on a forward stroke of the valve to communicate the inlet ports with the rear end surface area of the piston and adapted on a return stroke of the valve to communicate the discharge ports with said area; and wherein a motor has a driving connection with the valve for reciprocating the latter from one position to the other.
 7. An hydraulic rock drill as in claim 6, wherein the motor is hydraulically driven, and passage means is provided for causing flow of pressure fluid from the source to operate the motor.
 8. An hydraulic rock drill as in claim 7, wherein flow regulating means is provided in the passage means between the source and the motor.
 9. An hydraulic rock drill as in claim 1, including a rotation motor operable independently of the piston and having a rotary driving connection with the piston; wherein the first mentioned motor connected to reciprocate the valve is operable independently of any rotation that may be imparted to the piston by the rotation motor.
 10. An hydraulic rock drill as in claim 9, wherein the rotation motor is mounted to the housing in axial alignment with the cylinder and piston.
 11. An hydraulic rock drill comprising a housing, a piston cylinder in the housing, a piston hydraulically reciprocable in the cylinder having a piston rod portion adapted to have a drill string and rock bit attached thereto, a bulk oil accumulator chamber in the housing in surrounding relation to the cylinder providing a bulk source of constantly pressurized oil, the piston having a forward end surface of smaller area than its opposite rear end surface, a port communicating the accumulator chamber directly with the cylinder forwardly of the smaller area end of the piston and constantly exposing the latter end to the pressurized oil in the accumulator chamber; reciprocable valve means having a first port connection with the accumulator chamber, a second port connection with a discharge passage, and a common port communicating with the rear end surface of the piston; and a motor connected to reciprocate the valve means for a first position communicating the first port with the common port to a second position communicating the common port with the second port.
 12. An hydraulic rock drill as in claim 11, including a rotation motor having an output drive shaft means axially aligned with the piston, and the piston having an axially slidable driven spline connection with the drive shaft means, whereby the piston is enabled to have concurrently reciprocating axial movement relative to the drive shaft means and rotation with the drive shaft means.
 13. An hydraulic tool comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having a piston rod portion adapted to have work implement attached thereto, a source of pressurized hydraulic fluid, the piston having a forward end surface area subject to application of pressure fluid from the source to move the piston on a return stroke and having an opposite rear end of relatively greater surface area subject to application of pressure fluid from the source to move the piston on a work stroke, port means constantly exposing the forward end surface area of the piston to the pressure of fluid from the source, and power driven valve means for intermittently exposing the rear end surface area of the piston to the pressure to fluid from the source; wherein the valve means includes inlet ports for communicating the rear end surface area of the piston with the source, and discharge ports for communicating said area with a sump; wherein the valve means includes a reciprocable valve having a peripheral groove adapted on a forward stroke of the valve to communicate the inlet ports with the rear end surface area of the piston and adapted on a return stroke of the valve to communicate the discharge ports with said rear end surface area; and wherein a motor separate from and independent of the operation of the piston has a driving connection with the valve for reciprocating the latter from one position to the other.
 14. An hydraulic tool as in claim 13, wherein the tool includes a housing defining a bulk oil reservoir for the source of pressurized fluid, and the housing provides a bore in which the piston cylinder is located.
 15. An hydraulic tool as in claim 13, wherein the motor is hydraulically driven and passage means is provided for causing flow of pressure fluid from the source to operate the motor.
 16. An hydraulic tool as in claim 13, including a rotation motor having a rotary driving connection with the piston.
 17. An hydraulic tool comprising a piston cylinder, a piston hydraulically reciprocable in the cylinder having an externally extending piston rod adapted to have a work implement attached thereto, a housing providing a bulk reservoir of pressurized hydraulic fluid for effecting reciprocation of the piston, the piston having a front end subject to application of pressure fluid from the reservoir to drive the piston on a reTurn stroke and having an opposite rear end of a relatively greater area subject to application of pressure fluid from the reservoir to drive the piston on a work stroke, an outlet port connecting the reservoir with the cylinder constantly exposing the front end of the piston to the pressurized fluid of the reservoir, a second outlet port from the reservoir, a reciprocable control valve in the housing having a first position exposing the rear end area of the piston through the second outlet port to the pressure of fluid in the reservoir and having a reverse position exposing the rear end of the piston to a discharge port, and a motor separate from an operable independently of the piston to reciprocate the control valve from one position to the other.
 18. An hydraulic tool as in claim 17, wherein the power means is an hydraulically operable rotary motor drivingly connected with the control valve and having a conduit connection with the reservoir for allowing flow of pressurized fluid from the reservoir to operate the motor.
 19. An hydraulic tool as in claim 18, wherein a flow control regulator is provided in the conduit for regulating the operating speed of the motor and as a consequence the reciprocating frequency of the control valve. 